webapploader.java

webwork source

package webwork.view.velocity;

import java.io.InputStream;
import javax.servlet.ServletContext;

import org.apache.velocity.runtime.resource.loader.ResourceLoader;
import org.apache.velocity.runtime.resource.Resource;
import org.apache.velocity.exception.ResourceNotFoundException;
import org.apache.commons.collections.ExtendedProperties;

/**
 * Resource loader that uses the ServletContext of a webapp to
 * load Velocity templates.  (it's much easier to use with servlets than
 * the standard FileResourceLoader, in particular the use of war files
 * is transparent).
 * <p>
 * The default search path is '/' (relative to the webapp root), but
 * you can change this behaviour by specifying one or more paths
 * by mean of as many webapp.resource.loader.path properties as needed
 * in the velocity.properties file.
 * <p>
 * All paths must be relative to the root of the webapp.
 *<p>
 * NOTE: Shamelessly stolen from velocity-tools sources. We include
 * it because it's a lot more civilised that lugging in all of
 * velo-tools just for a resource loader.
 *
 * @author <a href="mailto:[e-mail]">Geir Magnusson Jr.</a>
 * @author <a href="mailto:[e-mail]">Nathan Bubna</a>
 * @author <a href="mailto:[e-mail]">Claude Brisson</a>
 * @version $Id: WebAppLoader.java,v 1.2 2003/11/16 04:54:53 fate Exp $
 */
public class WebAppLoader extends ResourceLoader
{

  /** The root paths for templates (relative to webapp's root). */
  protected String[] paths = null;

  protected ServletContext servletContext = null;

  /**
   *  This is abstract in the base class, so we need it.
   *  <br>
   *  NOTE: this expects that the ServletContext has already
   *        been placed in the runtime's application attributes
   *        under its full class name (i.e. "javax.servlet.ServletContext").
   *
   * @param configuration the {@link org.apache.commons.collections.ExtendedProperties} associated with
   *        this resource loader.
   */
  public void init(ExtendedProperties configuration)
  {
    rsvc.info("WebappLoader : initialization starting.");

    /* get configured paths */
    paths = configuration.getStringArray("path");
    if(paths == null || paths.length == 0)
    {
      paths = new String[1];
      paths[0] = "/";
    }
    else
    {
      /* make sure the paths end with a '/' */
      for(int i = 0; i < paths.length; i++)
      {
        if(!paths[i].endsWith("/"))
        {
          paths[i] += '/';
        }
        rsvc.info("WebappLoader : added template path - '" + paths[i] + "'");
      }
    }

    /* get the ServletContext */
    Object obj = rsvc.getApplicationAttribute(ServletContext.class.getName());
    if(obj instanceof ServletContext)
    {
      servletContext = (ServletContext)obj;
    }
    else
    {
      rsvc.error("WebappLoader : unable to retrieve ServletContext");
    }

    rsvc.info("WebappLoader : initialization complete.");
  }

  /**
   * Get an InputStream so that the Runtime can build a
   * template with it.
   *
   * @param name name of template to get
   * @return InputStream containing the template
   * @throws org.apache.velocity.exception.ResourceNotFoundException if template not found
   *         in  classpath.
   */
  public synchronized InputStream getResourceStream(String name) throws ResourceNotFoundException
  {
    InputStream result = null;
    if(name == null || name.length() == 0)
    {
      throw new ResourceNotFoundException("WebappLoader : No template name provided");
    }

    /* since the paths always ends in '/',
    * make sure the name never ends in one */
    while(name.startsWith("/"))
    {
      name = name.substring(1);
    }

    Exception exception = null;
    for(int i = 0; i < paths.length; i++)
    {
      try
      {
        result = servletContext.getResourceAsStream(paths[i] + name);

        /* exit the loop if we found the template */
        if(result != null)
        {
          break;
        }
      }
      catch(Exception e)
      {
        /* only save the first one for later throwing */
        if(exception == null)
        {
          exception = e;
        }
      }
    }

    /* if we never found the template */
    if(result == null)
    {
      String msg;
      if(exception == null)
      {
        msg = "WebappLoader : Resource '" + name + "' not found.";
      }
      else
      {
        msg = exception.getMessage();
      }
      /* convert to a general Velocity ResourceNotFoundException */
      throw new ResourceNotFoundException(msg);
    }

    return result;
  }

  /**
   * Defaults to return false.
   */
  public boolean isSourceModified(Resource resource)
  {
    return false;
  }

  /**
   * Defaults to return 0
   */
  public long getLastModified(Resource resource)
  {
    return 0;
  }
}